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Abstract:

A spiral spring (10) for the movement of a watch, includes a plurality of
coplanar leaves (10a, 10b) wound into one another. Furthermore, the inner
ends of each leaf are rigidly connected to a single collet (12). The
leaves (10a, 10b) and the collar (12) are produced as a single part.

Claims:

1-14. (canceled)

15. A spiral spring of a watch movement, including a plurality of
coplanar leaves wound into one another, wherein the inner ends of each
leaf being secured to a single collet, wherein the leaves, the collet are
made monolithically, and wherein the outer ends of each leaf are
connected to each other by a rigid frame provided with at least one
portion to receive an attachment organ, said frame, the leaves and the
collet being made monolithically, and wherein the last coil of the leaves
includes a reinforcement arranged so as to bring the center of gravity of
the active part to the action center of the elastic torque.

16. The spiral spring according to claim 15, including n leaves offset by
360.degree./n.

17. The spiral spring according to claim 16, wherein n is between 2 and 4
(bounds included).

18. The spiral spring according to claim 15, wherein the pitch of each
leaf is constant.

19. The spiral spring according to claim 16, wherein the pitch of each
leaf is constant.

20. The spiral spring according claim 17, wherein the pitch of each leaf
is constant.

21. The spiral spring according to claim 15, wherein the pitch of each
leaf is variable.

22. The spiral spring according to claim 16, wherein the pitch of each
leaf is variable.

23. The spiral spring according to claim 17, wherein the pitch of each
leaf is variable.

24. The spiral spring according to claim 15, wherein the frame includes
wide zones and at least one slim zone, said slim zone being intended to
receive a balance-spring stud to attach the spiral spring to the watch
movement.

25. The spiral spring according to claim 16, wherein the frame includes
wide zones and at least one slim zone, said slim zone being intended to
receive a balance-spring stud to attach the spiral spring to the watch
movement.

26. The spiral spring according to claim 17, wherein the frame includes
wide zones and at least one slim zone, said slim zone being intended to
receive a balance-spring stud to attach the spiral spring to the watch
movement.

27. The spiral spring according to claim 18, wherein the frame includes
wide zones and at least one slim zone, said slim zone being intended to
receive a balance-spring stud to attach the spiral spring to the watch
movement.

28. The spiral spring according to claim 21, wherein the frame includes
wide zones and at least one slim zone, said slim zone being intended to
receive a balance-spring stud to attach the spiral spring to the watch
movement.

29. The spiral spring according to claim 15, wherein the frame includes
at least one hole intended to receive a balance-spring stud to attach the
spiral spring to the watch movement.

30. The spiral spring according to claim 16, wherein the frame includes
at least one hole intended to receive a balance-spring stud to attach the
spiral spring to the watch movement.

31. The spiral spring according to claim 17, wherein the frame includes
at least one hole intended to receive a balance-spring stud to attach the
spiral spring to the watch movement.

32. The spiral spring according to claim 18, wherein the frame includes
at least one hole intended to receive a balance-spring stud to attach the
spiral spring to the watch movement.

33. The spiral spring according to claim 21, wherein the frame includes
at least one hole intended to receive a balance-spring stud to attach the
spiral spring to the watch movement.

34. The spiral spring according to claim 24, wherein the frame includes
at least one hole intended to receive a balance-spring stud to attach the
spiral spring to the watch movement.

35. The spiral spring according to claim 15, wherein the frame includes
hollowed out zones.

36. The spiral spring according to claim 15, wherein the frame forms a
circle whereof the center is the center of the spiral.

37. The spiral spring according to claim 15, wherein the frame forms an
arc of circle, with an angle that is a multiple of 360.degree./n.

38. The spiral spring according to claim 15, made with a base of silicon,
in particular monocrystalline silicon, possibly covered with a layer of
silica or a layer of diamond.

39. The spiral spring according to claim 15, made with a base of diamond,
obtained by growth, then by deep etching.

Description:

TECHNICAL FIELD

[0001] The present invention relates to the field of mechanical horology.
It more particularly relates to a spiral spring intended to equip a
regulator organ of a mechanical watch.

BACKGROUND OF THE INVENTION

[0002] In clocks, pendulums, and mechanical or electronic watches, there
is always a regulator organ making it possible, as its name indicates, to
regulate the running of the timepiece. In the case of a mechanical watch,
the regulator organ is formed by a balance and a spiral spring.

[0003] Traditionally, the spiral is a leaf, in general metal, with a
rectangular section wound on itself in the shape of a spiral of
Archimedes. It is fixed in its center on the balance-staff, by a piece
called a collet. The outside of the spiral is fixed to a balance, called
balance-cock, by a piece called a balance-spring stud. The balance-spring
stud is fixed either directly to the balance-cock, or via a mobile
balance-spring stud support.

[0004] Such an assembly of a spiral is not optimal for the isochronism of
the watch. In fact, the center of the spiral moves during its
development, which causes reaction forces at the pivots of the
balance-staff. The intensity of the forces exerted on the pivots
participates greatly in the isochronism that is generally observed.

[0005] Timepiece are known provided with two spirals mounted on the
balance-staff, in opposite directions, arranged in different planes. The
house H. Moser & Cie offers an escapement provided with two spirals
arranged on either side of the balance, in opposite directions. It is
known that it is difficult to obtain precise characteristics for spirals
made traditionally and that therefore, two spirals will most often be
different, even just slightly. Thus, the adjustment of such a balance
provided with two spirals having different characteristics, and the
alignment of the forces exerted by the two spirals, present difficulties.
Furthermore, the likely difference between the two spirals makes the
result of the forces exerted at the balance-staff, in most cases,
non-null and difficult to control.

[0006] The present invention therefore aims to propose a spiral making it
possible to improve the isochronism of a watch, while remaining simple to
implement.

BRIEF DESCRIPTION OF THE INVENTION

[0007] More specifically, the invention relates to a spiral spring of a
watch movement as defined in claim 1.

[0008] Other features of the invention are provided in the dependent
claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Other features of the present invention will emerge more clearly
upon reading the following description, done in reference to the appended
drawing, in which FIGS. 1 to 6 show, in top view, diagrammatic views of
different embodiments according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0010]FIG. 1 shows a flat spiral spring 10. It comprises a first inner
end associated with a collet 12.

[0011] Particularly to the invention, from the collet 12, several leaves
are deployed, the drawing showing two of them. There is therefore a first
10a and a second 10b leaf, wound in the same plane and in the same
direction. The leaves 10a and 10b are wound into one another, the coils
of one being inserted between the coils of the other. The first 10a and
second 10b leaves are arranged at 180° relative to one another.
The leaves are identical, so that the ends of the leaves are situated on
a circle and are situated at 180° from one another.

[0012] Advantageously, the outer ends of the leaves are connected to each
other by a rigid frame 14, i.e. the frame does not (or practically does
not) contribute to the elastic torque exerted by the spring. The shape of
the frame 14 is circularly symmetrical relative to the center of the
spiral. Preferably, the frame follows a circular path, concentric to the
spiral.

[0013] Typically, as allowed by shaping techniques with silicon-type
materials, the collet 12 is made in one piece with the rest of the
spiral. Advantageously, for the leaves to have identical elastic
characteristics, the two leaves 10a and 10b, the collet 12 and the frame
14 are made in a single piece, monolithically. To that end, the spiral
according to the invention can be made from materials that can be shaped
using deep etching techniques, particularly silicon-based spirals, in
particular made from monocrystalline silicon, potentially covered by a
layer of silica, but also spirals made from diamond, obtained by growth
then deep etching, or spirals made from DCS (Diamond Coated Silicon),
i.e. silicon spirals covered with diamond.

[0014] Owing to the symmetrical arrangement of two identical leaves 10a
and 10b, each of the leaves exerts a force on the balance-staff
offsetting the force exerted by the other leaf. Thus, the reactions on
the staff are minimized, or practically null, which makes it possible to
improve the isochronism of the oscillator.

[0015] The frame 14 is arranged to be able to support an attachment organ,
preferably a balance-spring stud, to connect the spiral to a
balance-spring stud fixed on the movement. In the embodiment of FIG. 1,
the frame has a portion with a width adapted to receive a slotted
balance-spring stud, known by those skilled in the art. More
specifically, the frame has a wide zone 14a and a slimmer zone 14b to
receive the balance-spring stud. The latter is fixed to the frame using
an adapted technique, such as adhesion or welding, chosen by one skilled
in the art.

[0016] FIGS. 2 to 5 propose different embodiments to produce the frame 14.
In FIGS. 2 to 4, the frame 14 is semi-circular and connects the two ends
of the leaves arranged at 180°. In FIG. 2, the wide zones 14a of
the frame are hollowed out, which makes it possible to lighten the spiral
in the outer zone thereof, which is always interesting to limit the
forces on the balance-spring stud in case of impact.

[0017] In FIG. 3, the frame 14 has several slim zones 14b, making it
possible to position the balance-spring stud at several locations around
the frame, which can provide flexibility for the construction of the
movement.

[0018]FIG. 4 proposes a frame provided with a hole 16 to receive a
non-slotted balance-spring stud, which can be housed and fixed in the
hole. The frame 14 of FIG. 5 is arranged in the same way, but makes a
full circle by connecting the outer ends of the leaves by their two
sides. The distribution of the masses is thus completely symmetrical. It
will be noted that, even in the configuration where the frame is provided
with a hole, the frame could be hollowed out. Several holes can also be
arranged on the frame.

[0019] It will also be noted that the function of the frame can be
fulfilled by a balance-cock including several balance-spring studs (one
balance-spring stud per leaf), making it possible to fix the ends of the
leaves. In that case, the frame, as such, is eliminated and only the
collet and the leaves are then monolithic.

[0020] Although the figures only show examples in which the spiral spring
10 includes two leaves, more can be provided. It is thus possible to have
n identical leaves, distributed at 360°/n around the collet, the
outer ends also being distributed at 360°/n. Such an arrangement
makes it possible to improve the distribution of the leaves and forces
around the balance-staff, and therefore allows better compensation.

[0021] In such a case, with n leaves, a frame 14 in the shape of an arc of
circle defines an angle of 360°/n, or a multiple of that value, as
chosen by the person skilled in the art. A complete circular frame is
also possible.

[0022] Each leaf being wound between the coils of other leaves, it is
understood that, for a spiral with a given dimension, increasing the
number of leaves causes, on the one hand, a reduction in the active
length of each leaf. Thus, relative to a conventional spiral occupying a
surface area S, provided with a single leaf whereof the active length is
L and thickness e (the thickness being the dimension of the leaf in the
plane of the spiral) and with pitch p between the coils, a spiral
according to the invention with n leaves of thickness e, pitch p for each
coil, occupying the same surface S, each leaf will have an active length
of length L/n. This consequently increases the stiffness of the leaf, but
that can be offset by decreasing the thickness of each leaf, which makes
it possible to increase the active length and decrease the stiffness. It
is thus easy to obtain a total desired torque in compliance with the
torques obtained with conventional spiral springs. It is also possible to
consider making spirals occupying a larger surface area in order to
obtain leaves with the desired length. From a practical perspective,
spirals with 2, 3 or 4 leaves will be preferred.

[0023]FIG. 6 proposes a spiral spring 10 whereof the outer coil of each
leaf is provided with a reinforcement 18 making it possible to correct
the centering of the spiral and to bring the center of gravity of the
active part to the action center of the elastic torque, i.e. to the
center of the spiral. Such a reinforcement 18 makes it possible to
improve the concentricity of the development of the spiral and to further
reduce the reactions at the pivot. It will be noted that the
reinforcement 18 in itself does not participate in defining the elastic
torque of the spiral. As shown in FIG. 6, the pitch separating the last
spire is at a constant distance from the next-to-last coil, including at
the reinforcement. It would also be possible to consider the distance
between the last coil and the next-to-last coil being smaller than the
pitch separating the other coils, particularly at the reinforcement.

[0024] This description was provided solely as a non-limiting illustration
of the invention and one skilled in the art can also provide various
alternatives following directly from the description provided above,
without going beyond the scope defined by the claims. In particular, the
pitch of each leaf can be constant, as shown in the drawing, but it can
also vary. Furthermore, the balance-spring stud can be replaced by
another fixing mode, in particular a screw to secure the frame directly
with the balance-cock.